Patterns of Transmission and Sources of Infection in Outbreaks of Human Toxoplasmosis

Abstract

We report on apparent temporal progression of probable sources of infection and transmission routes for global human toxoplasmosis outbreaks as described in published articles. We searched the Scientific Electronic Library Online, Web of Science, PubMed, and Scopus databases for articles on Toxoplasma, toxoplasmosis, and outbreaks. We found that transmission routes for Toxoplasma gondii varied by decade. In the 1960s and 1990s, toxoplasmosis outbreaks mainly occurred through ingestion of cysts in meat and meat derivatives; in the 1980s, through milk contaminated with tachyzoites; in 2000, due to the presence of oocysts in water, sand, and soil; and in 2010, due to oocysts in raw fruits and vegetables. Our study suggests a possible change in the epidemiology of reported toxoplasmosis outbreaks. Because of this change, we suggest that greater attention be paid to the disinfection of vegetables, as well as to the quality of water used for drinking and irrigation.

Keywords: Toxoplasma gondii; human; oocysts; outbreak; parasites; toxoplasmosis; vegetables; water.

Figure 1

Selection process for articles for systematic review of reports of outbreaks of human toxoplasmosis throughout the world during 1967–March 2018.

Figure 2

Geographic distribution of 34 outbreaks of human toxoplasmosis worldwide as cited in reports published during 1967–March 2018. Probable and known transmission routes are indicated by color. Circle size corresponds to the number of outbreaks.

Figure 3

Multiple correspondence analysis of the variables extracted from articles published on human toxoplasmosis outbreaks during 1967–March 2018. The multiple correspondence technique helps to visualize the multivariate relation between the categories of different variables. Proximity of the variables in the graph suggests a possible association between them.